Compound fluid meter

ABSTRACT

A compound fluid meter including a turbine type high flow metering device disposed in a main metering conduit, a low flow positive displacement metering device disposed in a bypass conduit connected to the main conduit, changeover valve means in said main conduit for preventing fluid flow therethrough when the fluid pressure is less than a predetermined pressure, the bypass conduit being adapted to receive fluid upstream from the valve means and reintroduce it downstream of the valve means, the turbine type high flow metering device comprising a fixed rodlike support member upon which an impeller is rotatably mounted, the rod-like support member having a free end extending towards the upstream end of the main conduit, a recess in said free end of the rod-like support member, a first thrust member loosely disposed in the recess and extending therefrom toward the upstream end of the main conduit, a ball-shaped thrust member and a recess in the hub of the impeller shaped to receive at least the free end of the rod-like support member with the first thrust member extending therefrom and the ball-shaped thrust member disposed between the upstream end of the hub recess and the first thrust member. Holes may be provided in the impeller for introducing the fluid being metered into the hub recess to lubricate and cool the relatively rotating elements therein. Further, face polarized annular permanent magnets are provided for coupling the impeller to an intermediate gear train and the intermediate gear train to the gearing of a register box to permit the intermediate gear train to be disposed in a fluid tight casing. Still further, the changeover valve means may comprise a toggle link mounted valve member having a cam follower adapted to cooperate with a cam for guiding the valve member through its opening and closing movements.

United States Patent Masson et al.

[ July 18, 1972 [54] COMPOUND FLUID METER Galnon-Calnet Industries,Inc., Newark, NJ.

[22] Filed: March 27, 1970 [2|] Appl.No.: 23,355

[73] Assignee:

[52] U.S. Cl ..73/197, 73/23l, 308/l 72, 308/174, l37/6l2 [51] Int. Cl...G01f 7/00 [58] Field olSearch ..73/l97, 229, 230, 23l,23l M; 308/ I68,172

[56] References Cited UNITED STATES PATENTS 934,504 9/l909 Connet..73/l97 l,l88,360 6/l9l6 Larrabee.... ..73/l97 l,245,740 l l/l9l7 Krieg..73/l97 1,842,267 1l/l932 Holmes ..73/l97 3,203,238 8/1965 Whittaker etal.. .....73/l97 3,342,070 9/1967 Walch, .lr ..73/23l 3,398,577 8/1968Kovats et al. ..73/23l Primary Examiner-Richard C. Queisser AssistantExaminer-John P. Beauchamp Attorney-Lerner, David & Littenberg lABSTRACT A compound fluid meter including a turbine type high flowmetering device disposed in a main metering conduit, a low flow positivedisplacement metering device disposed in a bypass conduit connected tothe main conduit, changeover valve means in said main conduit forpreventing fluid flow therethrough when the fluid pressure is less thana predetermined pressure. the bypass conduit being adapted to receivefluid upstream from the valve means and reintroduce it downstream of thevalve means, the turbine type high flow metering device comprising afixed rod-like support member upon which an impeller is rotatablymounted, the rod-like support member having a free end extending towardsthe upstream end of the main conduit, a recess in said free end of therod-like support member, a first thrust member loosely disposed in therecess and extending therefrom toward the upstream end of the mainconduit, a ball-shaped thrust member and a recess in the hub of theimpeller shaped to receive at least the free end of the rod-like supportmember with the first thrust member extending therefrom and theball-shaped thrust member disposed between the upstream end of the hubrecess and the first thrust member. Holes may be provided in the impeller for introducing the fluid being metered into the hub recess tolubricate and cool the relatively rotating elements therein. Further,face polarized annular permanent magnets are provided for coupling theimpeller to an intermediate gear train and the intermediate gear trainto the gearing of a register box to permit the intennediate gear trainto be disposed in a fluid tight casing. Still further, the changeovervalve means may comprise a toggle link mounted valve member having a camfollower adapted to cooperate with a cam for guiding the valve memberthrough its opening and closing movements.

27 Claims, 8 Drawing figures PATENIEU JUL 1 8 I972 FIG. 5

I.\"V1;'N1'()RS NARINDER MASSON WILLIAM J. KORENICKI WALTER L. LECHNERLERNER, DAVID a LITTENBERG ATTORNEYS PATENTED JUL 1 a ran 3" 577; 084

SHEET 3 BF 3 POSITIVE DISPLACEMENT OPENING OF 555 CHANGEOVER VALVE AP AFIG. 6

FLOW (6PM) [NVENTORS NARINDER MASSON WILLIAM J KORENICKI BY WALTER L.LECHNER LERNER, DAVID 8 LITTENBERG ATTORNEYS COMPOUND FLUID METERBACKGROUND OF THE INVENTION Compound fluid meters are well known asevidenced by U.S. Pat. No. 934,504 to F. N. Connet granted Sept. 21,1909; US. Pat. No. 2,425,720 to C. P. Bergman granted Aug. 19, 1947 andUS. Pat. No. 3,203,238 to A. R. Whittaker et al granted Aug. 31, I965.Compound fluid meters are used when it is desired to accurately recordthe entire range of fluid flow rates through conduits, such as largeservice pipes, from the smallest stream to full demand. Thus, compoundfluid meters generally comprise a high flow metering element disposed ina main conduit, a low flow metering element disposed in a bypassconduit, and changeover valve means for causing fluid flow past the highflow meter when the fluid pressure exceeds a predetermined high pressureand causing fluid flow past the low pressure flow meter when the fluidpressure is below the said predetermined high pressure. For example, thecompound fluid meter of the Whittaker et al patent comprises an impellertype high flow meter disposed in a main conduit, a nutating disc typelow flow meter disposed in a bypass conduit, and changeover valve meansfor preventing fluid flow through the main conduit until a predeterminedhigh pressure is reached. Fluid flow through the bypass conduit ispermitted at all times.

Though the compound fluid meter art is well developed, there is ofcourse always room for improvement in the provision of compound fluidmeters which exhibit improved operating characteristics, are lightweight, compact, require less and/or easier servicing, and are lessexpensive than present compound fluid meters.

SUMMARY OF THE INVENTION According to the present invention, there isprovided a compound fluid meter comprising a main conduit for receivingthe fluid to be metered, a turbine type high flow metering deviceincluding an impeller disposed in the main conduit, changeover valvemeans disposed in the main conduit downstream of the impeller adapted toblock fluid flow through the main conduit when the fluid pressure isbelow a predetermined high pressure and to permit fluid flowtherethrough when the fluid pressure is equal to or greater than thesaid predetermined high pressure, a bypass conduit for removing fluidfrom the main conduit at a point upstream from the valve means andreintroducing it into the main conduit downstream from the valve means,low flow positive displacement metering means for metering fluid flowthrough the bypass conduit, a support member rotatably supporting theimpeller in the main conduit, the support member having a free endextending toward the upstream end of the main conduit, a recess in saidfree end of said support member, a first thrust member disposed in andextending from said support member recess toward the upstream end of themain conduit, a second thrust member, and a recess in said impellershaped to receive at least the free end of the support member with thefirst thrust member extending therefrom and the second thrust memberdisposed between the downstream end of the impeller recess and the firstthrust member.

The invention further resides in the provision of lubricating holesextending through the impeller from the outside to the impeller recessfor introducing the fluid being metered into the impeller recess tolubricate and cool the relatively rotating elements therein.

The invention still further resides in the fact that the turbine typemetering device may comprise face polarized magnetic coupling means forcoupling the impeller to an intermediate gear train and the intermediategear train to the turbine meter's register box thereby permitting theintermediate gear train to be disposed in a fluid tight casing. Similarface polarized magnetic coupling means may be used for connecting therotating element of the low flow metering means with its register box.

The invention still further resides in the face that the changeovervalve means comprises a valve member, toggle link means mounting saidvalve member in the main conduit, said valve member comprising a camfollower, and a cam for cooperating with said cam follower to guide thevalve member through its opening and closing movements.

Still further features of the invention reside in the fact that theentire impeller assembly can be assembled employing press-fittechniques, the bearing thrust members can be case hardened and areeasily replaceable, and the turbine type metering device can be removedfor servicing without requiring removal of the main conduit from theline into which it is connected.

The general objects of this invention reside in the desire to provide acompound fluid meter which exhibits improved operating characteristics,is easier to manufacture, less expensive, more light weight, morecompact, and easier to service.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view of acompound fluid meter in accordance with the present invention;

FIG. 2 is a cross-section of the compound fluid meter of FIG. 1 takenalong the lines 2-2 of FIG. 1;

FIG. 3 is a plan view of a portion of the compound fluid meter of FIG.1;

FIG. 4 is an exploded view of the turbine wheel assembly of FIG. 1;

FIG. 5 is an exploded perspective view in part of the compound fluidmeter of FIG. 1 showing the turbine housing unit and impeller out of themain conduit;

FIG. 6 is a flow diagram illustrating the functioning of the changeovervalve;

FIGS. 7a, 7b and 7c are schematic illustrations of different positionsof the changeover valve assembly; and

FIG. 8 is a side elevational view partly in cross section of an impellertype metering device in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I which is across-sectional view of a compound fluid meter in accordance with thepresent invention, there is shown a main conduit 10 having an inlet end12 and an outlet end 14. The general arrangement of the componentswithin the main conduit 10 comprise an inlet guide assembly 16positioned adjacent the inlet end 12 and consisting of a generallybullet-shaped central portion I8 and radially disposed guide vanes 20,an impeller assembly 22 disposed downstream of the inlet guide assembly16, a fluid tight inter mediate gear casing 24 disposed downstream ofthe impeller assembly 22, and a changeover valve assembly 26 disposeddownstream of the intermediate gear casing 24. A somewhat tortuousbypass conduit 28 is connected to the main conduit 10 and comprises abypass inlet 30 disposed upstream of the valve assembly 26, bypasspassage means 32, and a bypass outlet 34 opening into the main conduitdownstream of the valve assembly 26. A nutating disc type low flow fluidmeter 27 is disposed in the bypass conduit 28 for metering fluid passingtherethrough.

Before describing the details of the compound fluid meter, it isbelieved that a general discussion of the various flow conditions,particularly the flow paths, will be helpful toward providing a readyand complete understanding of the invention. Referring to FIGS. 1, 3 an5, it can be seen that the inlet 30 leads to a circular grooved flowchannel 38. A pair of outlets 40 and 42 connect channel 38 to an inletchannel 44 which leads to the nutating disc 46 of the nutating disc typemeter 27. After passing by the disc 46, the fluid flows back into themain conduit 10 via the bypass outlet 34. The fore going descriptiondescribes fluid flow during low flow metering when the changeover valveassembly 26 is closed preventing direct flow through the main conduitl0.

When a predetermined high flow is reached, pressure differential causesthe changeover valve assembly 26 to open permitting fluid flow directlythrough the main conduit and past the vanes 48 of the impeller 50 of theturbine type metering device 22. Due to the quick action of the presentchangeover valve assembly 26, more fully described hereinafter,substantially all of the fluid flow immediately commences to passthrough the main conduit 10 so that the turbine type metering device 22approximates almost 100 percent accuracy and easily provides at leastthe minimum of 85 percent accuracy of registration required by AmericanWater Works Association Standards dated July 25, 1947. Registrationaccuracy is defined therein as the ratio in percent of the water flowmeasured by a meter as compared to the actual amount of water flowingthrough the meter.

The initial fluid flow pattern differs somewhat from the described highvolume and low volume flows. During start up, and assuming that initialfluid flow is at a low rate, the fluid, such as water, enters the inlet12 and moves through the inlet guide assembly past the impeller 50causing rotation thereof due to the interaction of the fluid with theimpeller vanes 48. However, almost immediately, main conduit 10 fills upwith fluid from the upstream face 52 of the valve member 54 of thechangeover valve assembly 26 to a position approximately adjacent thebypass inlet 30. Fluid flow then commences through the bypass conduit32. Fluid flow past the impeller 50 ceases and rotational movement is nolonger imparted to the impeller 50. This is of course due to the factthat the bypass inlet 30 is disposed upstream of the impeller vanes 48.

Many of the specific illustrated structural features of the presentcompound fluid meter are well known and will not be described in detailso as not to obscure the invention itself by the recitation of wellknown structural details. For example, many types of the nutating disctype meter assembly 27 are well known, as are a similar type of metercalled an oscillating iston meter. Further, many structures of theregister box 56 of the turbine type metering device 22 and the elementstherein are well known. In addition, the use of flanges on the ends ofthe main conduit 10 and securing bolts in various positions are wellknown and will not be further alluded to so that the invention itselfcan be clearly described.

Referring to FIGS. 1 and 4, the turbine wheel assembly 22 comprises anaxle or rod-like fixed support member 58 which is mounted in a recess 59of the intermediate casing 24 and projects therefrom toward the inletend 12 of main conduit 107 A bearing 60 disposed in a bearing sleeve 62is mounted on the support member 58 and rotatably supports the impeller50 thereon. A recess 64 is formed in the end of support member 58 andloosely receives a cylindrical thrust member or thrust pellet 66. Afurther thrust member or ball-shaped thrust hearing 68 is disposedbetween the thrust member 66 and the upstream end of a recess 70 in theimpeller 50. The recess 70 comprises a generally semi-spherical frontend 72 which matingly receives the ball-shaped thrust member 68. Manyalternatives are possible. For example, the bearing sleeve 62 may beeliminated and the bearing 60 directly press fit into the impeller 50for certain material combinations.

Lubricating channels or holes 74 in impeller 50 permit the fluid beingmetered to pass into the recess 70 and lubricate and cool the relativelyrotating elements therein. Hearing 60 is provided with a groove 75 forimproving the lubricating and cooling efiects of the fluid.

Thrust member 66 and 68 function to absorb the thrust imposed on theimpeller 50 by the fluid tending to force the impeller 50 into contactwith the intermediate gear casing 24. The use of ball-shaped thrustbearings is well known as evidenced by US. Pat. No. 2,770,l 3] to R. C.Sparling granted Nov. 13, 1956. They function to minimize the tendencyof an impeller to wobble or gyrate about its axis during rotation aboutan axle such as support member 58. Due to the size of the ball-shapedthrust member 68, it can readily be made of expensive wear resistantmaterials and/or case hardened. In accordance with the presentinvention, the second thrust member 66 in the form of a pellet or smallcylinder is loosely disposed in recess 64 between the ballshaped thrustmember and the support member 58. Due to the size of the second thrustmember 66, it can also be made of a relatively expensive wear resistantmaterial and/or case hardened. Such a wear resistant material maypreferably comprise tungsten carbide.

It has been found that the use of the second thrust member 66 results inimproved impeller operating characteristics including more accurateperformance and longer wear. Further, servicing or repair is simplifiedin that both thrust members 66 and 68 can be readily and easily replacedif necessary. it would of course be much more difficult to attempt toreplace an entire support member 58. However, replacement of the supportmember 58 itself is facilitated in accordance with the present inventionin that the support member 58 is mounted in the recess 59 by well knownpress-fit techniques so that it can be easily removed and replaced ifthis proves necessary.

The impeller assembly 22 further comprises an annular drive magnet 76received in an annular recess 78 of the impeller 50. Magnet 76 is apermanent magnet and is preferably made of ceramic material. The sleeve62 and support member 58 are preferably made of stainless steel. Theimpeller 50 is preferably made of a plastic material, such aspolypropylene which has a specific gravity approximating that of water.

Referring more specifically to FIG. 4, the simplified assembly of theimpeller assembly 22 will be described. The bearing 60 is mounted in thesleeve 62 by well known press-fit techniques. As noted previously, thesupport member 58 is mounted in the recess 59 of the intermediate gearcasing 24 by similar press-fit techniques. In addition, the inlet guideassembly 16 is mounted in the inlet end 12 of the main conduit 10 bysuch press-fit techniques.

After the support member 58 is mounted in the recess 59 and the bearing60 is mounted in the sleeve 62, the assembled bearing 60 and sleeve 62are slid onto the support member 58. The thrust member or pellet 66 isthen loosely placed in the support member recess 64. The ball-shapedthrust member 68 is positioned in the mating portion 72 of the recess 70of the impeller 50 and the assembled impeller 50 and thrust member 68slid over the sleeve 62 and outwardly extending thrust member 66 andpress-fit on the sleeve 62 to complete the impeller assembly. When soassembled, the impeller 50 will rotate with the sleeve 62 and bearing 60about the support member 58 with the downstream side 79 of the impelleradjacent to but not in contact with the upstream face 81 of intermediategear casing 24.

The retention of the impeller 50 on the support member 58 is aided byforces from the fluid flow and by the magnetic coupling of the annularmagnet 76 with a further annular magnet rotatably supported on a gearshaft 82 trunnioned in bearings 84 and 86 within intermediate gearbasing 24.

Gear shafi 82 is coaxial with support member 58. Magnets 76 and 80 areaxially or face polarized. This magnetic coupling of the magnets 76 and80 causes the horizontal shaft 82 to rotate at the same speed that theimpeller 50 rotates. A first bevel gear 88 is fixedly mounted on theshaft 82 and rotates therewith. First bevel gear 88 meshes with a secondbevel gear 90 fixedly mounted on a vertical shaft 92 which is trunnionedin bearings 94 and 96. A driven annular magnet 98 is fixedly mounted onthe upper end of the vertical shaft 92. The driven magnet 98 is alsoaxially or face polarized and is magnetically coupled with a registerbox annular drive magnet 100 mounted on a vertical shaft l02 which iscoaxial with the vertical shaft 92. Register box drive magnet 100 isthereby rotated at a speed proportional to the rotation of impeller 50and through well known gearing provides a meter reading in the registerbox 56 which is proportional to the fluid flow passed impeller 50.

Though the use of magnetic coupling techniques is well known in thepresent art, the present construction of axially or face polarized pairsof annular magnets 76, 80 and 98, [00 has been found to be particularlydesireable. As noted previously, the electromagnet coupling of annularmagnets 76 and 80 aid in retaining impeller 50 on the support member 58.In addition, improved magnetic coupling is achieved. Most importantly,the use of the axially or face polarized magnets has made it possible toinclude the entire intermediate gear assembly within the fluid tightgear casing 24. Gear casing 24 is sealed on the downstream end by afluid tight plug 104 sealing the opening 108, and a fluid tight plug 106seals the upper opening 109. The sealing plug 106 also functions as amagnetic spacing element in determining the spacing between magnets 98and 100. It will be noted that no shafts project out of intermediategear casing 24 thus eliminating the need for stuffing boxes, elaborateseals, or the like.

Servicing of the vertical shaft assembly 92 and its cooperating elementscan be easily accomplished by unscrewing of the threaded plug 106.Servicing of the horizontal shaft assembly 82 and its associatedelements can be easily accomplished by unscrewing of the threaded plug104. In fact, servicing of the entire turbine type metering device canbe readily accomplished as will be noted with regard to FIG. 5. Further,all internal components can be removed and serviced without removing themeter from the piping system. This includes both metering elements andthe valve elements.

It is believed to be clear from FIG. 5 that the entire turbine typemetering assembly can be easily removed from main conduit withoutrequiring removal of the main conduit from the line it is connected in.Thus, the entire turbine type metering device is suspended from a covermember 112 which can be easily vertically removed from main conduit 10by removal of the bolts (not shown) attaching it to main conduit 10. Itcan be seen in FIG. 1 that the register box 56 is mounted on cover 112.It will be noted that the turbine type metering device further comprisesa cowl-like member 111 which receives the impeller 50 and through whichthe fluid to be metered is passed to and around intermediate gear casing24 toward the valve member 54.

Assembly of the turbine type metering device with main conduit 10 isfacilitated by the provision of a U-shaped groove 113 (FIG. 5) whichreceives a soft gasket 114 (FIG. 1) adapted to sealingly receive avertical flange member 115 depending from cover 112. This simplifiedsealing means has proven to be effective, easy to service, and easy tomanufacture and assemble.

Referring to FIG. 8, where like reference numerals refer to similarparts, it will be noted that the present turbine type metering devicemay be employed alone. Though the construction of the turbine typemetering device is not changed, it will be appreciated that theconstruction of the main conduit 10' will differ from the constructionof main conduit 10 in that accommodation for the low flow meteringdevice, bypass conduit, etc. need not be made. With regard to theconstruction of the turbine type metering device in general, it can beclearly seen in FIG. 8 that the vanes 48 consist of helical blademembers 48 formed in an overlapping manner. The overlapping helicalblade design is preferred as it has been found to provide improvedaccuracy.

The changeover valve assembly 26 will initially be described withreference to FIGS. 1 and 2. A valve seat 116 is formed in main conduit10 downstream from intermediate gear casing 24. All fluid flow directlythrough main conduit 10 must pass through valve seat 116. Valve member54 comprises a valve sealing insert member 118 which seals valve seat116 when valve member 54 is disposed in the fully closed position shownin FIG. 1. Insert member 118 is made of resilient material which aids ineffecting a good seal.

Valve member 54 is mounted for toggle action movement as will bedescribed. Such movement is provided for by two pairs of cooperatingtoggle links 119, 120 and 121, I22; stops 128 disposed above one end ofeach link 120 and 122; an elongated pin member 132 disposed near the topof valve member 54; and an elongated slot 130 which receives elongatedpin member 132. It will be noted that links 119 and 121 are pivotallymounted at one end to shaft 124 and at their other ends to links and 122respectively. It will also be noted that links 120 and 122 are pivotallyconnected to pin 126 and extended beyond the valve member 54 in theupstream direction for engagement with the stops 128. As will be broughtout more fully hereinafter, the present arrangement has resulted in morerapid action of the valve member 54.

Guide means in the form of a cam follower or roller 134 and a cam orramp 136 are provided for guiding valve member 54 through its openingand closing positions. The cam follower 134 and cam 136 also providepositive stops for determining the valve fully opened and fully closedpositions. The guide means have been found to be effective in insuringpositive action of the changeover valve assembly 26 and more rapidopening and closing movements. In particular, it has been found that theclosing movements of the valve member 54 are more rapid and precise whenemploying the guide means.

Ramp 136 is fixedly secured in main conduit 10 centrally of the valvemember 54 by four screws 138. To remove the entire ramp assembly, thescrews 138 can be removed and the ramp 136 also removed without removingmain conduit 10 from the rest of the piping. The cam surface of ramp 136includes a knee 140 which defines the valve member 54 fully closedposition, a smooth guiding surface 142 for guiding the cam follower 134through the opening and closing movements of the valve member 54, and anabutment 144 which defines the fully opened position of valve member 54.It will be noted that the knee 140 of the cam surface permits an initialslightly vertical movement of valve member 54 while it is maintained inits fully closed position. Such initial vertical movement is alsoaccommodated by slot and the cooperating elongated pin member 132. Infact, the cooperating slot 130 and pin I32 and the cooperating roller134 and knee 140 act together in defining an initial path of verticalmovement for valve member 54. Further, a valve roller rest is providedto insure that the most desirable functioning relationship of ramp 136and roller 134 will be obtained every time the valve member 54 isbrought to the fully closed position.

A characteristic curve 146 illustrative of the fluid pressure (abscissa)against the upstream face 52 of valve member 54, which is similar to thepressure on nutating disc 46, versus fluid flows in gallons per minute(GPM) (ordinate) is shown in FIG. 6. The point A represents the desiredflow at which the changeover valve assembly 26 will operate to permitfluid flow through main conduit 10 thereby actuating the high flowturbine type meter. The nutating disc type meter 27 measures flow atrates below the desired valve opening point and is very accurate withinthe range of flows that it is used to measure. The high flow turbinetype meter is very accurate within the range of expected flows betweenthe flow at the desired valve opening point and the full demand expectedin the line. The pressure acting on valve member 54 increases until thepredetermined flow rate (point A) is reached. Then, as the valve opens,the pressure rapidly drops off to the point C, where valve member 54 isin its fully open position, and then commences to rise with increasingflow.

FIGS. 70, 7b and 7c are schematic illustrations of the changeover valveassembly 26 in its fully closed position, an intermediate position, andits fully open position, respectively. When the valve member 54 is inthe closed position, fluid pressure acting on the valve face 52 willdevelop a moment (AP) (rra'l4) (h) tending to open the valve, where h isthe vertical distance between points 124 and 126 and d is the diameterof valve seat 1 16.

The moment resisting the opening of valve member 54 is its weight Wtimes the distance L from the point 124 to the point 126. When APbecomes sufficiently large (point A in FIG. 6), valve member 54 andlinks 119, 120 and 121, 122 will rotate slightly clockwise about point124. The valve member 54 will lift vertically bringing cam follower 134to the upper portion of the knee of cam 136 and pin 132 to the lowerportion of slot 132. Thus, initial vertical movement of valve member 54while it is in its fully closed position is accommodated.

Upon further vertical movement of valve member 54, cam follower 134 willreach the top of the knee 140 and, simultaneously, links 120 and 122will engage stops 128. Such engagement causes the links 120 and 122 tomove counterclockwise about pivot point 150 thereby breaking the toggleaction of the pairs of links 119, 120 and 121, 122. At this instant, themoment resisting opening of valve member 54 is (W) (f), where frepresents the horizontal distance between the center of gravity ofvalve member 54 and pin 132. it will be appreciated that the distance fis much less than the distance L. Further, the moment tending to movevalve member 54 to its fully opened position is (AP) (mP/4) (y), where yis the vertical distance between the center of valve seat 116 and pin132. it will be appreciated that the distance y is greater than thedistance h. Thus, while the moment tending to move valve member 54 toits fully open position has increased, the moment tending to hold valvemember 54 in its closed position has greatly decreased. Therefore, valvemember 54 rapidly moves to its fully open position shown in FIG. 7c.

A reduction in fluid flow results in valve member 54 moving towards itsfully closed position. Upon approaching its fully closed position, areverse toggle action occurs and the valve member rapidly moves to itsfully closed position.

The cam follower 134 and cam 136 guide valve member 54 at all timesthrough its opening and closing movements. This insures the desiredmovement of valve member 54 and has provided increased reliability ofperformance. In addition, more rapid opening and closing has resulted.

Referring again to FIGS. 1 and 2, it will be noted that the pairs oflinks 119, 120 and 121, 122 are provided with stops 152 and 156,respectively. Further, the pivot 150 referred to in FIGS. 70, 7b and 7cis provided by pivot pin 150 for links 119, 120 and by pivot pin 154 forlinks 121, 122. The stops 152 and 156 are engaged by extensions 158 and160 of links 120 and 122 respectively to define the fully closedpositions of the pairs of links respectively.

While the principles of the invention have been described in connectionwith specific apparatus, it is to be clearly understood that thedescription is made only by way of example and not intended as alimitation to the scope of the invention as set forth in theaccompanying claims.

What is claimed is:

l. A compound fluid meter comprising:

a main conduit having an inlet end for receiving the fluid to be meteredand an outlet end for discharging the metered fluid;

a turbine type high flow metering device including an impeller assemblydisposed in said main conduit, said impeller assembly including animpeller, a support member rotatably supporting said impeller in saidmain conduit, said support member having a free end extending towardsthe inlet end of said main conduit, an impeller recess in said impellershaped to receive at least the free end of said support member, and saidimpeller comprises fluid channels extending from the outside of saidimpeller to said impeller recess whereby the fluid being metered maypass into said impeller recess for lubrication and cooling of therelatively rotating parts therein;

changeover valve means disposed in said main conduit downstream fromsaid impeller assembly and adapted to block fluid flow through said mainconduit when the fluid pressure is below a predetermined high pressureand to permit fluid flow therethrough when the fluid pressure is equalto or greater than said predetermined high pressure;

bypass conduit means including a bypass conduit, an inlet thereto fromsaid main conduit for removing fluid from said main conduit upstreamfrom said valve means, and an outlet therefrom into said main conduitdownstream of said valve means; and

low flow metering means disposed in said bypass conduit for meteringfluid flow therethrough.

2. A meter according to claim 1, wherein said support member comprisesan axle member, and said impeller assembly comprises an annular bearingmember mounted on said axle member and having an inner diameter suchthat it is retained on said axle member, a cylindrical sleeve memberdisposed about said annular bearing member and having an inner diametersuch that said annular bearing member is retained in said sleeve member,and said impeller recess includes a cylindrical portion receiving saidsleeve member and having a diameter such that said sleeve member isretained therein.

3. A meter according to claim 1, wherein said fluid channels compriseholes extending from the upstream end of said impeller to said impellerrecess.

4. A meter according to claim 1, wherein said support member comprises arod-like support member and said turbine type high pressure meteringdevice comprises a support member mounting recess shaped to tightlyreceive and retain an end of said rod-like support member.

5. A meter according to claim 1, wherein said turbine type high flowmetering device comprises a liquid impervious intermediate gear casingdisposed in said main conduit downstream from said impeller, saidsupport member comprises arod-like support member extending from saidcasing, a first shafi is rotatably mounted in said casing approximatelycoaxial with said support member, a first permanent magnet is alfixed tosaid first shaft and disposed adjacent the portion of said casing fromwhich said support member extends, and a second permanent magnet isaffixed to said impeller and disposed adjacent said casing inmagnetically coupled relationship with said first magnet.

6. A meter according to claim 5, wherein said turbine type high flowmetering device comprises a second shaft rotatably mounted in saidliquid impervious intermediate gear casing, means connecting said secondshaft to said first shaft to rotate said second shaft at a rateproportional to the rotation of said first shaft, :1 third permanentmagnet affixed to said second shaft, and a register box including flowindicator means and flow indicator drive means, said flow indicatordrive means comprising a rotatably mounted fourth permanent magnetdisposed in magnetically coupled relationship with said third magnet.

7. A meter according to claim 5, wherein said magnets are annularlyshaped.

8. A meter according to claim 6, wherein said magnets are annularlyshaped.

9. A meter according to claim 6, wherein said first shaft ishorizontally disposed, said second shaft is vertically disposed, andsaid means connecting said first and second shafts comprises a pair ofmiter gears.

10. A meter according to claim 6, wherein said casing comprises anopening disposed adjacent said third magnet and a plug member sealinglyclosing said opening, said plug member being made of non-magneticmaterial and being shaped to space the third and fourth magnets apredetermined distance apart.

11. A meter according to claim 6, wherein said low flow metering meanscomprises a nutating disc type meter including a nutating disc disposedin said bypass conduit, a rotatably mounted shaft driven by saidnutating disc, a fifth permanent magnet afiixed to said driven shaft, alow flow register box including low flow indicator means and low flowindicator drive means, and a liquid impervious wall disposed betweensaid low flow register box and said nutating disc, said low flowindicator drive means including a sixth permanent magnet rotatablymounted in magnetically coupled relationship with said fifth magnet.

12. A meter according to claim 1, wherein said turbine type high flowmetering device includes an intermediate gear casing mounted adjacentsaid impeller assembly, and a cover member, said impeller assembly andintermediate gear casing being fixedly connected to said cover member,and said main conduit comprises an opening through which saidintermediate gear casing and impeller assembly can be passed to theirOperating positions, said cover being adapted to seal said opening andsimultaneously position said intermediate gear casing and said impellerassembly in their operating positions.

13. A compound fluid meter comprising:

a main conduit having an inlet end for receiving the fluid to be meteredand an outlet end for discharging the metered fluid;

a turbine type high flow metering device including an impeller assemblydisposed in said main conduit, said turbine type high flow meteringdevice further including an intermediate gear casing mounted adjacentsaid impeller assembly, and a cover member, said impeller assembly andintermediate gear casing being fixedly connected to said cover member,said main conduit comprises an opening through which said intermediategear casing and impeller assembly can be passed to their operatingpositions, said cover being adapted to seal said opening andsimultaneously position said intermediate gear casing and said impellerassembly in their operating positions, a generally U-shaped flangemember projecting from said cover member and extending around saidimpeller assembly, said main conduit including a U-shaped sealing grooveadapted to receive said U-shaped flange member, and a soft gasket isdisposed in said U-shaped sealing groove for sealingly receiving saidU-shaped flange member;

changeover valve means disposed in said main conduit downstream fromsaid impeller assembly and adapted to block fluid flow through said mainconduit when the fluid pressure is below a predetermined high pressureand to permit fluid flow therethrough when the fluid pressure is equalto or greater than said predetermined high pressure;

bypass conduit means including a bypass conduit, an inlet thereto fromsaid main conduit for removing fluid from said main conduit upstreamfrom said valve means, and an outlet therefrom into said main conduitdownstream of said valve means; and

low flow metering means disposed in said bypass conduit for meteringfluid flow therethrough.

l4. A meter according to claim 13, wherein said turbine type high flowmetering device includes a register box, and said cover member comprisesmeans for mounting said register box thereon.

l5. A meter according to claim I, wherein said changeover valve meansincludes a valve seat through which fluid flow to the outlet end of saidmain conduit must pass, a valve member for sealing said valve seat,toggle action means mounting said valve member in said main conduit fortoggle action movement between a closed valve seat sealing position andan open valve seat non-obstructing fluid flow position, and guide meansfor guiding said valve member through its valve seat opening and closingmovements.

16. A compound fluid meter comprising:

a main conduit having an inlet end for receiving the fluid to be meteredand an outlet end for discharging the metered fluid;

a turbine type high flow metering device including an impeller assemblydisposed in said main conduit, said impeller assembly including animpeller, a support member rotatably supporting said impeller in saidmain conduit, said support member having a free end extending towardsthe inlet end of said main conduit, and an impeller recess in saidimpeller shaped to receive at least the free end of said support member;

changeover valve means disposed in said main conduit downstream fromsaid impeller assembly and adapted to block fluid flow through said mainconduit when the fluid pressure is below a predetermined high pressureand to permit fluid flow therethrough when the fluid pressure is equalto or greater than said predetermined high pressure;

said changeover valve means includes a valve seat disposed in agenerally vertical plane through which fluid flow to the outlet end ofsaid main conduit must pass, a valve member for sealing said valve seat,and toggle action means mounting said valve member in said main conduitfor toggle action movement between a closed valve seat sealing positionand an open valve seat non-obstructing fluid flow position, said toggleaction means including a first link pivotally connected to said valvemember, a second link pivotally connected at one end to said first linkat a position disposed below and downstream from the pivotal connectionof said first link to said valve member, said second link beingpivotally connected at its other end to said main conduit at a positiondisposed below and downstream from the pivotal connection of said secondlink to said first link, said first and second links being axiallyaligned when said valve member is in its closed position, and a stopmember disposed above said first link and positioned to engage saidfirst link when said valve member is moved vertically a predetermineddistance causing said first link to pivot about its pivotal connectionto said second link in a counterclockwise direction;

bypass conduit means including a bypass conduit, an inlet thereto fromsaid main conduit for removing fluid from said main conduit upstreamfrom said valve means, and an outlet therefrom into said main conduitdownstream of said valve means; and

low flow metering means disposed in said bypass conduit for meteringfluid flow therethrough.

17. A meter according to claim 16, wherein a portion of said first linkextends beyond said valve member in the upstream direction and said stopmember is positioned to engage with said upstream extending portion.

18. A meter according to claim l6, wherein one of said first and secondlinks comprises an abutment and the other of said first and second linkscomprises a finger portion which engages said abutment when said valvemember is in its fully closed position and the first and second linksare axially aligned.

19. A meter according to claim 16, wherein said valve member includes avertical slot disposed above said pivotal connection of said valvemember to said first link, and further comprising a horizontal pinmember cooperating with said vertical slot to permit both initialvertical movement of the valve member while it is in its fully closedposition and pivoting movement of the valve member about said horizontalpin member.

20. A meter according to claim 19, further comprising guide means whichcooperate with said horizontal pin member and vertical slot to constrainsaid valve member to vertical movement while in its fully closedposition until said first link engages said stop member.

21. A meter according to claim 20, wherein said guide means comprisescam follower means mounted on said valve member and cam meanscooperating with said cam follower means for guiding said valve memberthrough its valve seat opening and closing movements.

22. A meter according to claim 21, wherein said cam follower meanscomprises a roller rotatably mounted on said valve member.

23. A meter according to claim 2l, wherein said cam means comprises agenerally vertically disposed ramp-like member, and said ramp-likemember includes an initial vertically disposed portion which cooperateswith said cam follower means and said vertical slot and horizontal pinmember to constrain said valve member to said vertical movement prior tosaid engagement of said first link with said stop member.

24. A meter according to claim 23, wherein said ramp like membercomprises a final abutment portion which defines the fully open positionof said valve member.

25. A meter according to claim 23, wherein said toggle action meansincludes two pairs of said first and second links pivotally connected tosaid valve member one on each side of said rampclike member.

26. A compound fluid meter comprising:

a main conduit having an inlet end for receiving the fluid to be meteredand an outlet end for discharging the metered fluid;

a turbine type high flow metering device including an impeller assemblydisposed in said main conduit, said impeller assembly including animpeller, a support member rotatably supporting said impeller in saidmain conduit, said support member having a free end extending towardsthe inlet end of said main conduit, and an impeller recess in saidimpeller shaped to receive at least the free end of said support member;

changeover valve means disposed in said main conduit downstream fromsaid impeller assembly and adapted to block fluid flow through said mainconduit when the fluid pressure is below a predetermined high pressureand to permit fluid flow therethrough when the fluid pressure is equalto or greater than said predetermined high pressure;

said changeover valve means includes a valve seat through which fluidflow to the outlet end of said main conduit must pass, a valve memberfor sealing said valve seat, toggle action means mounting said valvemember in said main conduit for toggle action movement between a closedvalve seat sealing position and an open valve seat non-obstructing fluidflow position, and guide means for guiding said valve member through itsvalve seat opening and closing movements, said guide means includingmeans for mounting said valve member for limited vertical movement, camfollower means mounted on said valve member, and a generally verticallydisposed ramplike member in operative relationship with said camfollower means, said ramp-like member including a lower initial verticalportion adapted to permit initial vertical movement of the valve memberwithout unseating of the valve member;

bypass conduit means including a bypass conduit, an inlet thereto fromsaid main conduit for removing fluid from said main conduit upstreamfrom said valve means, and an outlet therefrom into said main conduitdownstream of said valve means; and

low flow metering means disposed in said bypass conduit for meteringfluid flow therethrough.

27. An assembly according to claim 26, wherein said toggle action meansincludes a vertical slot in said valve member and a horizontal pinmember which cooperates with said vertical slot to constrain said valvemember to vertical movement only while said cam follower means is inengagement with said initial vertical portion of said ramp-like member.

1. A compound fluid meter comprising: a main conduit having an inlet endfor receiving the fluid to be metered and an outlet end for dischargingthe metered fluid; a turbine type high flow metering device including animpeller assembly disposed in said main conduit, said impeller assemblyincluding an impeller, a support member rotatably supporting saidimpeller in said main conduit, said support member having a free endextending towards the inlet end of said main conduit, an impeller recessin said impeller shaped to receive at least the free end of said supportmember, and said impeller comprises fluid channels extending from theoutside of said impeller to said impeller recess whereby the fluid beingmetered may pass into said impeller recess for lubrication and coolingof the relatively rotating parts therein; changeover valve meansdisposed in said main conduit downstream from said impeller assembly andadapted to block fluid flow through said main conduit when the fluidpressure is below a predetermined high pressure and to permit fluid flowtherethrough when the fluid pressure is equal to or greater than saidpredetermined high pressure; bypass conduit means including a bypassconduit, an inlet thereto from said main conduit for removing fluid fromsaid main conduit upstream from said valve means, and an outlettherefrom into said main conduit downstream of said valve means; and lowflow metering means disposed in said bypass conduit for metering fluidflow therethrough.
 2. A meter according to claim 1, wherein said supportmember comprises an axle member, and said impeller assembly comprises anannular bearing member mounted on said axle member and having an innerdiameter such that it is retained on said axle member, a cylindricalsleeve member disposed about said annular bearing member and having aninner diameter such that said annular bearing member is retAined in saidsleeve member, and said impeller recess includes a cylindrical portionreceiving said sleeve member and having a diameter such that said sleevemember is retained therein.
 3. A meter according to claim 1, whereinsaid fluid channels comprise holes extending from the upstream end ofsaid impeller to said impeller recess.
 4. A meter according to claim 1,wherein said support member comprises a rod-like support member and saidturbine type high pressure metering device comprises a support membermounting recess shaped to tightly receive and retain an end of saidrod-like support member.
 5. A meter according to claim 1, wherein saidturbine type high flow metering device comprises a liquid imperviousintermediate gear casing disposed in said main conduit downstream fromsaid impeller, said support member comprises a rod-like support memberextending from said casing, a first shaft is rotatably mounted in saidcasing approximately coaxial with said support member, a first permanentmagnet is affixed to said first shaft and disposed adjacent the portionof said casing from which said support member extends, and a secondpermanent magnet is affixed to said impeller and disposed adjacent saidcasing in magnetically coupled relationship with said first magnet.
 6. Ameter according to claim 5, wherein said turbine type high flow meteringdevice comprises a second shaft rotatably mounted in said liquidimpervious intermediate gear casing, means connecting said second shaftto said first shaft to rotate said second shaft at a rate proportionalto the rotation of said first shaft, a third permanent magnet affixed tosaid second shaft, and a register box including flow indicator means andflow indicator drive means, said flow indicator drive means comprising arotatably mounted fourth permanent magnet disposed in magneticallycoupled relationship with said third magnet.
 7. A meter according toclaim 5, wherein said magnets are annularly shaped.
 8. A meter accordingto claim 6, wherein said magnets are annularly shaped.
 9. A meteraccording to claim 6, wherein said first shaft is horizontally disposed,said second shaft is vertically disposed, and said means connecting saidfirst and second shafts comprises a pair of miter gears.
 10. A meteraccording to claim 6, wherein said casing comprises an opening disposedadjacent said third magnet and a plug member sealingly closing saidopening, said plug member being made of non-magnetic material and beingshaped to space the third and fourth magnets a predetermined distanceapart.
 11. A meter according to claim 6, wherein said low flow meteringmeans comprises a nutating disc type meter including a nutating discdisposed in said bypass conduit, a rotatably mounted shaft driven bysaid nutating disc, a fifth permanent magnet affixed to said drivenshaft, a low flow register box including low flow indicator means andlow flow indicator drive means, and a liquid impervious wall disposedbetween said low flow register box and said nutating disc, said low flowindicator drive means including a sixth permanent magnet rotatablymounted in magnetically coupled relationship with said fifth magnet. 12.A meter according to claim 1, wherein said turbine type high flowmetering device includes an intermediate gear casing mounted adjacentsaid impeller assembly, and a cover member, said impeller assembly andintermediate gear casing being fixedly connected to said cover member,and said main conduit comprises an opening through which saidintermediate gear casing and impeller assembly can be passed to theiroperating positions, said cover being adapted to seal said opening andsimultaneously position said intermediate gear casing and said impellerassembly in their operating positions.
 13. A compound fluid metercomprising: a main conduit having an inlet end for receiving the fluidto be metered and an outlet end for discharging the metered fluid; aturbine type high flow metering device including an iMpeller assemblydisposed in said main conduit, said turbine type high flow meteringdevice further including an intermediate gear casing mounted adjacentsaid impeller assembly, and a cover member, said impeller assembly andintermediate gear casing being fixedly connected to said cover member,said main conduit comprises an opening through which said intermediategear casing and impeller assembly can be passed to their operatingpositions, said cover being adapted to seal said opening andsimultaneously position said intermediate gear casing and said impellerassembly in their operating positions, a generally U-shaped flangemember projecting from said cover member and extending around saidimpeller assembly, said main conduit including a U-shaped sealing grooveadapted to receive said U-shaped flange member, and a soft gasket isdisposed in said U-shaped sealing groove for sealingly receiving saidU-shaped flange member; changeover valve means disposed in said mainconduit downstream from said impeller assembly and adapted to blockfluid flow through said main conduit when the fluid pressure is below apredetermined high pressure and to permit fluid flow therethrough whenthe fluid pressure is equal to or greater than said predetermined highpressure; bypass conduit means including a bypass conduit, an inletthereto from said main conduit for removing fluid from said main conduitupstream from said valve means, and an outlet therefrom into said mainconduit downstream of said valve means; and low flow metering meansdisposed in said bypass conduit for metering fluid flow therethrough.14. A meter according to claim 13, wherein said turbine type high flowmetering device includes a register box, and said cover member comprisesmeans for mounting said register box thereon.
 15. A meter according toclaim 1, wherein said changeover valve means includes a valve seatthrough which fluid flow to the outlet end of said main conduit mustpass, a valve member for sealing said valve seat, toggle action meansmounting said valve member in said main conduit for toggle actionmovement between a closed valve seat sealing position and an open valveseat non-obstructing fluid flow position, and guide means for guidingsaid valve member through its valve seat opening and closing movements.16. A compound fluid meter comprising: a main conduit having an inletend for receiving the fluid to be metered and an outlet end fordischarging the metered fluid; a turbine type high flow metering deviceincluding an impeller assembly disposed in said main conduit, saidimpeller assembly including an impeller, a support member rotatablysupporting said impeller in said main conduit, said support memberhaving a free end extending towards the inlet end of said main conduit,and an impeller recess in said impeller shaped to receive at least thefree end of said support member; changeover valve means disposed in saidmain conduit downstream from said impeller assembly and adapted to blockfluid flow through said main conduit when the fluid pressure is below apredetermined high pressure and to permit fluid flow therethrough whenthe fluid pressure is equal to or greater than said predetermined highpressure; said changeover valve means includes a valve seat disposed ina generally vertical plane through which fluid flow to the outlet end ofsaid main conduit must pass, a valve member for sealing said valve seat,and toggle action means mounting said valve member in said main conduitfor toggle action movement between a closed valve seat sealing positionand an open valve seat non-obstructing fluid flow position, said toggleaction means including a first link pivotally connected to said valvemember, a second link pivotally connected at one end to said first linkat a position disposed below and downstream from the pivotal connectionof said first link to said valve member, said second link beingpivotally connected at its other end to said main conduit at a positioNdisposed below and downstream from the pivotal connection of said secondlink to said first link, said first and second links being axiallyaligned when said valve member is in its closed position, and a stopmember disposed above said first link and positioned to engage saidfirst link when said valve member is moved vertically a predetermineddistance causing said first link to pivot about its pivotal connectionto said second link in a counterclockwise direction; bypass conduitmeans including a bypass conduit, an inlet thereto from said mainconduit for removing fluid from said main conduit upstream from saidvalve means, and an outlet therefrom into said main conduit downstreamof said valve means; and low flow metering means disposed in said bypassconduit for metering fluid flow therethrough.
 17. A meter according toclaim 16, wherein a portion of said first link extends beyond said valvemember in the upstream direction and said stop member is positioned toengage with said upstream extending portion.
 18. A meter according toclaim 16, wherein one of said first and second links comprises anabutment and the other of said first and second links comprises a fingerportion which engages said abutment when said valve member is in itsfully closed position and the first and second links are axiallyaligned.
 19. A meter according to claim 16, wherein said valve memberincludes a vertical slot disposed above said pivotal connection of saidvalve member to said first link, and further comprising a horizontal pinmember cooperating with said vertical slot to permit both initialvertical movement of the valve member while it is in its fully closedposition and pivoting movement of the valve member about said horizontalpin member.
 20. A meter according to claim 19, further comprising guidemeans which cooperate with said horizontal pin member and vertical slotto constrain said valve member to vertical movement while in its fullyclosed position until said first link engages said stop member.
 21. Ameter according to claim 20, wherein said guide means comprises camfollower means mounted on said valve member and cam means cooperatingwith said cam follower means for guiding said valve member through itsvalve seat opening and closing movements.
 22. A meter according to claim21, wherein said cam follower means comprises a roller rotatably mountedon said valve member.
 23. A meter according to claim 21, wherein saidcam means comprises a generally vertically disposed ramp-like member,and said ramp-like member includes an initial vertically disposedportion which cooperates with said cam follower means and said verticalslot and horizontal pin member to constrain said valve member to saidvertical movement prior to said engagement of said first link with saidstop member.
 24. A meter according to claim 23, wherein said ramp-likemember comprises a final abutment portion which defines the fully openposition of said valve member.
 25. A meter according to claim 23,wherein said toggle action means includes two pairs of said first andsecond links pivotally connected to said valve member one on each sideof said ramp-like member.
 26. A compound fluid meter comprising: a mainconduit having an inlet end for receiving the fluid to be metered and anoutlet end for discharging the metered fluid; a turbine type high flowmetering device including an impeller assembly disposed in said mainconduit, said impeller assembly including an impeller, a support memberrotatably supporting said impeller in said main conduit, said supportmember having a free end extending towards the inlet end of said mainconduit, and an impeller recess in said impeller shaped to receive atleast the free end of said support member; changeover valve meansdisposed in said main conduit downstream from said impeller assembly andadapted to block fluid flow through said main conduit when the fluidpressure is below a predetermined high pressure and to permit fluid flowtherethrough when the fluid pressure is equal to or greater than saidpredetermined high pressure; said changeover valve means includes avalve seat through which fluid flow to the outlet end of said mainconduit must pass, a valve member for sealing said valve seat, toggleaction means mounting said valve member in said main conduit for toggleaction movement between a closed valve seat sealing position and an openvalve seat non-obstructing fluid flow position, and guide means forguiding said valve member through its valve seat opening and closingmovements, said guide means including means for mounting said valvemember for limited vertical movement, cam follower means mounted on saidvalve member, and a generally vertically disposed ramp-like member inoperative relationship with said cam follower means, said ramp-likemember including a lower initial vertical portion adapted to permitinitial vertical movement of the valve member without unseating of thevalve member; bypass conduit means including a bypass conduit, an inletthereto from said main conduit for removing fluid from said main conduitupstream from said valve means, and an outlet therefrom into said mainconduit downstream of said valve means; and low flow metering meansdisposed in said bypass conduit for metering fluid flow therethrough.27. An assembly according to claim 26, wherein said toggle action meansincludes a vertical slot in said valve member and a horizontal pinmember which cooperates with said vertical slot to constrain said valvemember to vertical movement only while said cam follower means is inengagement with said initial vertical portion of said ramp-like member.